NASA Rover Halfway to Huge Crater on Mars

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Two
years after setting out for a big Martian crater that could hold clues about
the Red Planet's potential to support life, NASA's rover Opportunity has hit a
milestone: It's more than halfway there.

Opportunity
turned its wheels toward the Endeavour crater in August 2008, after exploring
another crater, Victoria, for about two years. But Endeavour is a different
beast; at 14 miles (22 km) wide, it will be the biggest crater a NASA rover has
ever seen up close.

"We
are actually beyond halfway," said Matt Golombek,
chairman of the Mars rover science operations working group at NASA's Jet
Propulsion Laboratory.

Get
to the clay

Opportunity
landed on Mars with its twin rover, Spirit, in January 2004. Their missions
were supposed to last only about three months, but both far surpassed that
lifetime. Spirit got bogged down in soft sand in 2009 and stopped
communicating with Earth in spring of this year. Opportunity, though, is
still going strong.

NASA
scientists are keen for the rover to reach Endeavour. Last year, the agency's
Mars Reconnaissance Orbiter spacecraft detected clay deposits on the crater's
rim. Clay-bearing rocks are a strong indication of the past presence
of water, which is necessary for life as we know it.

In
fact, NASA's next Mars rover, the car-sized Curiosity, will prioritize looking
at clays. The rover is scheduled to launch in November 2011 and land on Mars in
August 2012. All of its potential landing sites sport clays similar to those
found on Endeavour's rim, Golombek said.

Another
intriguing aspect of Endeavour's clay is its age. The terrain surrounding
Endeavour dates to about four billion years ago, Golombek
said around the time when life likely started on Earth. Mars may have been
more conducive to life back then, and such old rocks could tell us more.

Scientists
also have a general interest in Martian
craters, clay-bearing or not. Big holes in the ground allow researchers to
peer beneath the top layers of dirt much deeper than
rovers' robotic arms can dig.

"You
can use craters as a poor-man's probe into the subsurface," Golombek said. "You can often see actual strata or
outcrop on their upper rims."

Still
chugging along

It's
taken Opportunity about two years to go 6 miles (10 km), so the rover won't be
reaching Endeavour for a while. Its travels are of the slow-but-steady variety.

"On
a really good day, we can go about 100 meters [330 feet]," Golombek said. "A short day is maybe half of
that."

Still,
there's no reason to think Opportunity won't make it, he said. The rover is in
pretty good shape, besides a broken right front wheel that doesn't turn. For
that reason, engineers are driving it backward, but that shouldn't pose a
problem.

"We're
not seeing anything that's going to stop us," Golombek
said.

If
Opportunity doesn't reach to Endeavour, it should still gather some useful data
along the way.

"Even
if we don't make it, we're going through some tremendously interesting
landscapes," Golombek said.